PSR-7 Storage-less HTTP Sessions
PSR7Session is a PSR-7 and
PSR-15
compatible middleware that enables
session without I/O usage in PSR-7 based applications.
Proudly brought to you by ocramius, malukenho and lcobucci.
Installation
composer require psr7-sessions/storageless
Usage
You can use the PSR7Sessions\Storageless\Http\SessionMiddleware in any
PSR-15
compatible middleware.
In a zendframework/zend-expressive
application, this would look like following:
$app = \Zend\Expressive\AppFactory::create();
$app->pipe(\PSR7Sessions\Storageless\Http\SessionMiddleware::fromSymmetricKeyDefaults(
'mBC5v1sOKVvbdEitdSBenu59nfNfhwkedkJVNabosTw=', // replace this with a key of your own (see docs below)
1200 // 20 minutes
));
After this, you can access the session data inside any middleware that
has access to the Psr\Http\Message\ServerRequestInterface attributes:
$app->get('/get', function (ServerRequestInterface $request, ResponseInterface $response) : ResponseInterface {
/* @var \PSR7Sessions\Storageless\Session\Data $session */
$session = $request->getAttribute(SessionMiddleware::SESSION_ATTRIBUTE);
$session->set('counter', $session->get('counter', 0) + 1);
$response
->getBody()
->write('Counter Value: ' . $session->get('counter'));
return $response;
});
You can do this also in asynchronous contexts and long running processes,
since no super-globals nor I/O are involved.
It is recommended that you use a key with lots of entropy, preferably
generated using a cryptographically secure pseudo-random number generator
(CSPRNG). You can use the CryptoKey tool
to do this for you.
Note that you can also use asymmetric keys by using either the
PSR7Sessions\Storageless\Http\SessionMiddleware constructor or the named
constructor PSR7Sessions\Storageless\Http\SessionMiddleware::fromAsymmetricKeyDefaults()
Examples
Simply browse to the examples directory in your console, then run
php -S localhost:9999 index.php
Then try accessing http://localhost:9999: you should see a counter
that increases at every page refresh
WHY?
In most PHP+HTTP related projects, ext/session serves its purpose and
allows us to store server-side information by associating a certain
identifier to a visiting user-agent.
What is the problem with ext/session?
This is all fair and nice, except for:
- relying on the
$_SESSIONsuperglobal - relying on the shutdown handlers in order to "commit" sessions to the
storage - having a huge limitation of number of active users (due to storage)
- having a lot of I/O due to storage
- having serialized data cross different processes (PHP serializes and
de-serializes$_SESSIONfor you, and there are security implications) - having to use a centralized storage for setups that scale horizontally
- having to use sticky sessions (with a "smart" load-balancer) when the
storage is not centralized - not designed to be used for multiple dispatch cycles
What does this project do?
This project tries to implement storage-less sessions and to mitigate the
issues listed above.
Assumptions
- your sessions are fairly small and contain only few identifiers and
some CSRF tokens. Small means< 400bytes - data in your session is
JsonSerializableor equivalent - data in your session is freely readable by the client
How does it work?
Session data is directly stored inside a session cookie as a JWT token.
This approach is not new, and is commonly used with Bearer tokens in
HTTP/REST/OAuth APIs.
In order to guarantee that the session data is not modified, that the
client can trust the information and that the expiration date is
mutually agreed between server and client, a JWT token
is used to transmit the information.
The JWT token is always signed to ensure that the user-agent is never
able to manipulate the session.
Both symmetric and asymmetric keys are supported for signing/verifying
tokens.
Advantages
- no storage required
- no sticky sessions required (any server having a copy of the private or
public keys can generate sessions or consume them) - can transmit cleartext information to the client, allowing it to share
some information with the server (a standard example is about sharing the
"username" or "user-id" in a given session) - can transmit encrypted information to the client, allowing server-only
consumption of the information - not affected by PHP serialization RCE attacks
- not limited to PHP process scope: can have many sessions per process
- no reliance on global state
- when in a multi-server setup, you may allow read-only access to servers
that only have access to public keys, while writes are limited to
servers that have access to private keys - can be used over multiple dispatch cycles
Configuration options
Please refer to the configuration documentation.
Known limitations
Please refer to the limitations documentation.
Contributing
Please refer to the contributing notes.
License
This project is made public under the MIT LICENSE.